SH/T 0625-1995 Determination of γ-Al₂O₃ Content in Silica-Alumina Catalysts (X-ray Diffraction Method)

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Card type: Test method

1. Method number / full name / English name / replacement relationship

• Standard number: SH/T 0625-95
• Chinese name: Determination of γ-Al₂O₃ Content in Silica-Alumina Catalysts (X-ray Diffraction Method)
• English name: not provided in the available source
• Replacement relationship: not provided in the available source (the text contains multiple adoption notes stating "the original standard required...", but the replaced standard number is not given)
• Other: approved by 1995-08-14, implemented by 1995-12-01; (confirmed in 2004)
• Equivalent adoption: ASTM D4926-89(1994) "Determination of γ-Al₂O₃ Content in Silica-Alumina Catalysts by X-ray Diffraction"

2. Scope of application and non-applicability

• This standard specifies a method for determining the relative content of γ-Al₂O₃ and other transition-state aluminas in silica-alumina catalysts using an X-ray diffractometer.
• Applicable to catalysts containing silicon oxide, aluminum oxide, aluminum silicate (including amorphous aluminum silicate, kaolin, or aluminum silicate molecular sieves).
• Not applicable: no explicit exclusion clause is provided in the available source. However, 3.2 points out that certain other components may cause interference, such as α- quartz, aluminum silicate molecular sieves, aluminum-based spinels formed at high temperature, etc.; the presence of large amounts of heavy metals or rare earth elements may also cause more serious interference.

3. Method principle

A calcined and finely ground catalyst sample is subjected to CuKα as the radiation source and other specified test conditions to collect 2θ-angle 50°~55° and 62°~73° two ranges of X-ray diffraction patterns (the first range diffraction pattern is used only as the background intensity before the measured peak when determining the second range diffraction pattern), and by calculating the net diffraction peak intensity ratio of the sample and the γ-Al₂O₃ reference sample at an 2θ angle of about 67°, the relative content of γ-Al₂O₃ in the sample is obtained.

3.1 considers that the broad diffuse diffraction peak appearing near 2θ angle 67° is formed by γ-Al₂O₃, suitable for evaluating the relative content of γ-Al₂O₃ in calcined catalysts, which may include the three forms of Al₂O₃ described in the literature as η, χ, and γ. δ-Al₂O₃ also has diffraction peaks in the same range, but generally forms above 800℃, and the treatment temperature of most catalysts is not higher than this temperature. The results given by this standard are collectively referred to as γ-Al₂O₃.

4. Reagents and materials (purity / preparation)

• γ-Al₂O₃ reference sample: a highly crystalline pseudo-boehmite sample is selected, prepared by calcination at 550℃ for 3h, and its γ-Al₂O₃ crystal phase content is certified as 100%.
• Note: The γ-Al₂O₃ reference sample is provided by the standardization technical focal point unit.
• Adoption note: The original standard used a fine-grained pure boehmite sample.

5. Instruments and equipment

• 4.1 X-ray powder diffractometer: uses a CuKα radiation source, nickel filter, and sample holder of the same specification. Divergence slit 2°, receiving slit 0.6mm, anti-scatter slit 2°. The test conditions to be selected when collecting X-ray diffraction patterns are shown in the table below.
• 4.2 Calcination furnace: working temperature can reach 800℃.
• 4.3 Grinding equipment: can grind the sample to a particle size of 75–38μm (200–400 mesh).

Adoption notes: 1] The original standard required collecting a 2θ-angle 52°~76° range of X-ray diffraction pattern. 2] The original standard required the use of a monochromator and corresponding slits, and required selection of a gain factor. This standard requires the use of a filter and relatively wide various slits, does not require re-selection of gain conditions under normal instrument operation, adopts two-range scanning and matching test conditions to collect diffraction data, and specifies the minimum net peak height of the reference sample.

6. Recommended operating conditions

Notes: ① The minimum full scale selected is 2000CPS, and the two range diffraction patterns must have the same range. ② The tube voltage and tube current values are determined according to the X tube power, the range, and the reference sample diffraction peak height (the net peak height must reach more than 60% of full scale); the tube voltage and tube current values used for the two range diffraction patterns must be the same. ③ When the full scale selected is 2000CPS, the tube voltage and tube current are selected at the maximum values allowed by the instrument, and the net peak height of the reference sample diffraction peak still cannot reach more than 60% of full scale, then the diffractometer is considered unable to meet the measurement requirements of this standard.

7. Sampling and sample preparation

• 6.1 The sample is calcined at 500℃ for 3h (for catalyst samples that have already undergone activation treatment above 500℃ or industrial operation, this step may be omitted; however, if these samples are obviously damp, they need to be dried).
• 6.2 Grind the sample to a particle size of 75~38μm, then press the sample into the sample holder for measurement.
• 6.3 Press three sample pellets for each sample and repeat the measurement, taking the average value; the γ-Al₂O₃ reference sample has good repeatability, and generally only needs to be measured once when continuously measuring a group of samples.

8. Analysis procedure

• According to the requirements of clause 4.1, select the recording mode and test conditions, perform two-range scanning, and collect the diffraction patterns of the sample and the γ-Al₂O₃ reference sample.
• For the data processing procedure, refer to the γ-Al₂O₃ diffraction schematic diagram (the original figure number is not provided in the available source, source-text extraction is "schematic diagram 21", requires confirmation against the source standard (source-text extraction)).
• 7.1 Determine the background intensity before and after the measured diffraction peak: from a position in each range diffraction pattern with no interfering diffraction peak (preferably the middle position), the background intensity b₁ can be obtained; from the end of the second range diffraction pattern (i.e., near 73°) at a position with no interfering diffraction peak, the background intensity after the measured diffraction peak b₂ can be obtained; mark the intensities of the two points b₁ and b₂ at the corresponding positions on the ordinate of the second range diffraction pattern; the midpoint of b₁ and b₂ is b₃, and b₃ is taken as the intensity of the background before the measured diffraction peak (at 2θ angle 62° position).
• 7.2 On the second range diffraction pattern, draw a straight line through b₃ and b₂ as the baseline of the measured diffraction peak, and based on this baseline, measure the net peak height H(s) and the peak half-height width W(s) of the sample diffraction peak.
• 7.3 Using the same method with the two lines 7.1 and 7.2, measure the net peak height H(r) and the peak half-height width W(r) of the γ-Al₂O₃ reference sample diffraction peak.
• 7.5 For samples with low γ-Al₂O₃ content (generally referring to below 20%), interference from other components on the measured diffraction peak becomes a prominent problem, and sometimes the exact position of the measured diffraction peak profile is difficult to determine; in this case, using the peak height ratio instead of the peak area ratio [i.e., omitting the W(s)/W(r) term in the formula of clause 7.4] will give better repeatability. However, there is a systematic error between the results obtained thereby and the results obtained from peak area, and when reporting results, "peak height method" must be noted.
• 7.6 As needed, different X-ray diffraction laboratories may select a γ-Al₂O₃ second reference sample. However, considering the comparability of data between laboratories, the γ-Al₂O₃ reference sample used in this standard must be used to calibrate the second reference sample and obtain the conversion factor.

9. Qualitative and quantitative and calculation formula

7.4 The relative mass percentage content of γ-Al₂O₃ X[%(m/m)] is calculated according to the following formula:

The original formula source-text extraction is severely incomplete, and only the following symbols can be identified: H(s), W(s), F(s), H(r), W(r), F(r).

Where:

• F(s)—— Full scale reading when recording the sample diffraction pattern CPS;
• F(r)—— Full scale reading when recording the γ-Al₂O₃ reference sample diffraction pattern CPS.

Adoption notes: 1] The G(r)/G(s) term in the original standard calculation formula is replaced by the [source-text extraction incomplete, requires confirmation against the source standard (source-text extraction)] term of this standard. 2] The original standard required calculation of peak area in all cases.

Note: The complete calculation formula cannot be accurately restored due to source-text extraction noise, requires confirmation against the source standard (source-text extraction).

10. Precision

Regardless of whether the results are calculated by peak area or by the peak height method, the following provisions are used to judge the reliability of the results (95% confidence level).

• 8.1 Repeatability: The repeatability of measurement results in the same laboratory is ±15% of the measurement average.
• 8.2 Reproducibility: The reproducibility of measurement results between different laboratories is ±2.4% of the measurement average.

11. Report

• Each sample is measured three times repeatedly, and the arithmetic average is taken as the measurement result.
• Results calculated from the peak height ratio must be noted as "peak height method".
• For results measured using a second reference sample, when comparing data between laboratories, the second reference sample number and conversion factor must be noted.

12. Referenced documents

No independent referenced documents section is provided in the available source. The text mentions reference to ASTM D4926-89(1994).

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Q&A